No shear gas key and carrier system

ABSTRACT

A shear resistant bolt carrier and gas key are provided having a mating recoil lug and recoil lug slot that transfer shear forces between the gas key and bolt carrier to reduce and eliminate shear forces on the screw attachment points and eliminate a point of failure in the bolt carrier group (“BGC”).

Applicant hereby claims priority under 35 USC § 119 to provisional U.S. patent application Ser. No. 62/919,904, filed Apr. 4, 2019, entitled “No Shear Gas Key and Carrier System.” The entire contents of the aforementioned application are herein expressly incorporated by reference.

FIELD

The present innovations generally relate to a bolt carrier group in a firearm, and more specifically to an arrangement for a bolt carrier and gas key that eliminates or reduces the risk of shearing the mounting screws.

BACKGROUND

Auto-loading firearms are well known in the art and include rifles as well as pistols. For example, M-16, AR-15, AR-10 type rifles and pistols auto-load by using gas pressure resulting from the burning gasses produced by a fired cartridge in the weapon to drive a bolt carrier group (“BCG”). This type of auto-loading system is known in the industry as a “gas impingement system.” The amount of gas flow into the system is predetermined by the size of a gas port hole in the bolt carrier portion of the BCG and the size of the gas port hole in the barrel of the weapon. The gas produced by the burning powder from the fired cartridge travels down the barrel, through the gas port in the barrel, into the gas tube which extends into a gas key, and bolt carrier as described in further detail below.

The cycling of the BCG ejects a spent cartridge, cocks the hammer, strips a new cartridge from the magazine, and loads the new cartridge into the chamber of the firearm. The BCG includes a bolt, a cam pin, a gas key, and a bolt carrier. As discussed above, in a typical gas impingement system the cycling of the BCG is accomplished using the gases caused by the burning of the propellant material, gunpowder, from the cartridge in the barrel after the cartridge is fired. Once loaded into the chamber of the firearm the cartridge is initially held in place by the bolt face and a set of lugs on the bolt that interact with lugs in the chamber of the firearm. Down the barrel from the chamber of the firearm is a gas port that is drilled into the top of the barrel at a location prior to the muzzle. The gas port is covered by a gas block which includes a gas channel aligned with the gas port. The gas channel of the gas block is connected to a gas tube which extends from the gas block back toward the chamber of the firearm and inserts into the gas key when the BCG is fully forward and in battery. The gas key has a gas passage typically extending from an inlet portion at a forward facing portion at the front of the gas key and extending through the gas key to an outlet portion on the bottom surface of the gas key. The bottom surface of the gas key mates with a top surface on the bolt carrier so that the outlet portion of the gas passage aligns with a gas hole in the bolt carrier. The gas hole is in communication with a gas chamber formed by a tail end of the bolt, a set of bolt gas rings, and an internal space in the bolt carrier when the BCG is fully forward in battery. The purpose of the gas passage is to form a pathway to move the gas traveling through the gas tube into the bolt carrier. The gas key is typically affixed to the top of the bolt carrier with two screw oriented perpendicular to the travel direction of the BCG.

In operation, when the firing pin strikes the primer in the cartridge the gunpowder ignites. The burning of the propellant expands the cartridge case and forces the lugs on the bolt, and in the chamber of the firearm, to lock thus sealing that end of the barrel while the projectile begins to move down the barrel propelled by the gases produced from the burning gunpowder. The gases expand and propel the projectile down the barrel toward the muzzle. Once the projectile passes the gas port in the barrel, and while it is still in the barrel, the gases sealed between the back of the projectile and the cartridge case flow up through the barrel gas port, through the gas channel in the gas block and into the gas tube. The gases in the gas tube then flow into the gas key, through its gas passage, through the gas hole in the bolt carrier and into the gas chamber formed by the tail end of the bolt, a set of bolt gas rings, and an internal space in the bolt carrier. When the pressure in the gas chamber reaches a sufficient level the bolt carrier is forced away from the bolt which in turn causes the cam pin to move and rotate the bolt thereby unlocking the bolt lugs from the chamber lugs and unlocking the bolt, which is driven along with the rest of the bolt carrier group back from the chamber of the firearm. This also drives the gas key away from the gas tube as the entire BCG moves backward from the chamber of the firearm. When the bullet exits the muzzle and the rest of the gases are expelled out of the muzzle. The BCG moves forward to strip another cartridge from the magazine and load it into the chamber of the firearm thereby reloading the firearm and completing a cycle.

The pressure produced by the expanding gas is in excess of 60,000 PSI. Because known gas keys are typically held in place on the bolt carrier by two screws, these two screws absorb all the shear force produce by the high pressure gas. This is a common failure point in the system. When these screws break or fail, the rifle is inoperable and generally cannot be repaired in the field.

For the foregoing reasons, it is desirable to provide an enhanced system for minimizing and eliminating the failure of the screws securing the gas key to the bolt carrier in firearms to allow for reliable cycling of the BCG, particularly in AR15, AR10, M16 and M4 type firearms.

SUMMARY

The present disclosure solves the above needs and deficiencies with known BCGs by providing a mating recoil lug and recoil lug slot on the gas key and bolt carrier. Specifically, the present disclosure provides a recoil lug on the gas key between two screw holes and a corresponding recoil lug slot between two screw holes on the bolt carrier. In this arrangement the recoil lug engages the recoil lug slot whereby the lateral, shear forces of the cycle are at least in part transferred between the two parts by the recoil lug rather than at the screw interface. In this way shear forces on the screws are minimized or eliminated, and screw failure is significantly minimized and eliminated. In alternate embodiments of the disclosure, the positioning of the recoil lug and recoil lug slot may be arranged to one side or the other of the two screw attachments, rather than in the middle of the two screw attachments. In yet other embodiments the recoil lug may be on the bolt carrier and the recoil lug slot may be on the gas key. In various other embodiments, the recoil lug and recoil lug slot are mating matching shapes, and may include a square, rectangle, square, octagonal, pentagon, oval, circular or combination of the above with sharp, chamfered or rounded corners for most efficient transfer of lateral forces. In various embodiments the recoil lug and recoil lug slot may be integrally molded or cut, respectively, into the gas key and bolt carrier while in other embodiments a slot may be cut in the gas key and bolt carrier for receipt of a pin which for example extends and protrudes through a slot cut in the gas key to form the recoil lug received in the recoil lug slot of the bolt carrier or vice versa. In the arrangements as proposed and with a longitudinal axis in the direction of BCG travel, the screws secure the gas key to the bolt carrier from separating in a direction perpendicular to the longitudinal axis and the shear absorption components (e.g., recoil lug and slot) of the gas key and bolt carrier prevent the gas key and bolt carrier from moving independently in the longitudinal direction. The shear absorption components preferably do not prevent perpendicular movement.

While the disclosure above and the detailed disclosure below is presented herein in the context of a particular bolt carrier and gas key, it will be understood by those of ordinary skill in the art that the concepts may be applied to other types of BGCs in various ways where there is a beneficial advantage to minimize and eliminate BCG failures due to shear forces. With the foregoing overview in mind, specific details will now be presented, bearing in mind that these details are for illustrative purposes only and are not intended to be exclusive.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various non-limiting examples and innovative aspects of the shear resistant bolt carrier and gas key in accordance with the present description:

FIG. 1 shows an isometric exploded view from the upper side of one embodiment of the bolt carrier and gas key;

FIG. 2 shows an isometric view from the underside of one embodiment of the gas key.

DETAILED DESCRIPTION

simplified overview, an improved bolt carrier and gas key are described herein for minimizing and eliminating BCG failure due to shear forces during the firing cycle. For example, the present disclosure is directed to a BCG having a bolt carrier fitted with gas key wherein the gas key has an integral recoil lug incorporated into the bottom side of the key to receive and transfer the shear force produced by the high pressure gas. The recoil lug shall fit into a female recoil lug slot or hole cut into the bolt carrier of sufficient size and dimensions to allow the lug to fit into the slot. The gas key may be held in position by the two screws just as in the current system, however, the screws will no longer take the shear force. The shear force will instead be transferred in whole or in part between the gas key and bolt carrier by the recoil lug and recoil lug slot interface, thus eliminating the possibility of broken screws.

An embodiment of the BCG bolt carrier and gas key components is shown in FIGS. 1 and 2. The bolt carrier 10 is shown without a bolt inserted into the bolt carrier 10 and without the gas key 30 attached to the top of the bolt carrier 10. As shown in FIG. 1, the bolt carrier 10 extends from a forward end to a rearward end to define a longitudinal axis. The bolt carrier 10 includes an upper surface for receiving a gas key 30. The upper surface has a pair of bolt carrier screw holes 12 used to secure the gas key 30, to the bolt carrier 10, and a recoil lug slot or hole 14 disposed in a space between the two screw holes. Adjacent to one of the screw holes 12 is a gas hole 16 in the upper surface of the bolt carrier 10. Referring to FIGS. 1 and 2, the gas key 30 extends from a forward end to a reward end along a longitudinal axis parallel to the longitudinal axis of the bolt carrier when installed. On a rearward portion of the gas key, there are two gas key screw holes 32 extending through the gas key in a direction perpendicular to the longitudinal axis from an upper surface to a lower surface of the gas key. Disposed on the lower surface of the gas key is also a recoil lug 34 positioned between the screw holes. The recoil lug 34 may be integrally molding with the gas key 30 or be formed as a replaceable pin inserted in a receiving hole in the gas key 30. The gas key 30 further includes a gas channel or passage 36 extending from an inlet portion at the forward end of the gas key 30 to and outlet portion on the lower or bottom surface of a rearward portion of the gas key 30. The outlet portion of the gas passage 36 is disposed adjacent to a screw hole 12.

The gas key recoil lug 34 is preferably sized, shaped and arranged, to be received in the bolt carrier recoil lug slot 14 when the gas key 30 is fitted to the bolt carrier 10, and the screw holes 32 of the gas key 30 and screw holes 12 of the bolt carrier 10 are arrange so that they are aligned to receive securing screws (not shown) to secure the gas key 30 to the bolt carrier 10. In this arrangement the bolt carrier gas hole 16 is also adapted and arranged to align with the outlet of the gas channel or passage 36 on the bottom of the gas key 30 when the gas key 30 is secured to the bolt carrier 10 using the screw holes 12. The gas hole 16 is in communication with a gas chamber (not shown), formed by a tail end of the bolt (not shown), a set of bolt gas rings (not shown), and an internal space 24 in the bolt carrier 10. Also present on the bolt carrier 10 is a hammer clearance slot 22, which permits the hammer (not shown) to extend into the bolt carrier 20 and strike a firing pin (not shown).

In this arrangement the gasses produced by the burning powder from the fired cartridge travels down the barrel, through the gas port in the barrel, into the gas tube which extends into the gas passage 36 of the gas key 30, which forms a pathway to move the gas traveling through the gas tube (not shown) into the bolt carrier 10. The high pressure gas which may exceed 60,000 PSI is used to force the BCG backward, putting high shear forces on the interface between the gas key 30 and bolt carrier 10. In the disclosed embodiments these shear forces are received and transferred between the gas key 30 and bolt carrier 10 through shear absorption components the recoil lug 34 and recoil lug slot 14, thus eliminating or reducing any shear force on the securing screws (not shown) in screw holes 12 and 32, and eliminating or minimizing any risk of failure of the securing screws (not shown).

While as depicted in the illustrative embodiment, the recoil lug 34 and recoil lug slot 14 are formed in mating rectangular shapes with rounded or chamfered corners, in alternate embodiments the recoil lug 34 and recoil lug slot 14 may be in a circular, triangular, square, hexagon, pentagon, T or X shaped or other shapes with either sharp, rounded or chamfered corners. While the illustrative embodiment also depicts the recoil lug 34 and recoil lug slot 14 as being disposed between the screw holes 12 and 32, in other embodiments the placement of the recoil lug 34 and recoil lug slot 14 may be in other arrangement where the screw hole pairs 12 and 32 are adjacent one another and the recoil lug 34 and recoil lug slot 14 are adjacent to the out let of the gas passage 36 and gas hole 16, respectively. In yet other embodiments this may be reversed so that the recoil lug 34 is most distant from the outlet of the gas passage 36 and the recoil lug slot 14 is most distant from the gas hole 16. In further alternate embodiments, the arrangement of the recoil lug 34 and recoil lug slot 14 may be reversed so that the recoil lug 34 may be on the bolt carrier 10, and the recoil lug slot 14 may be on the gas key 30. In yet further alternate embodiments the bolt carrier 10 may include more than one recoil lug 34 or recoil lug slots 14 or a combination of a recoil lugs 34 and recoil lug slots 14, and have mating reciprocal recoil lugs 34 and/or recoil lug slots 14 on the gas key 30.

It should be understood that this description (including the figures) is only representative of some illustrative embodiments. For the convenience of the reader, the above description has focused on representative samples of all possible embodiments, and samples that teach the principles of the disclosure. The description has not attempted to exhaustively enumerate all possible variations. That alternate embodiments may not have been presented for a specific portion of the disclosure, or that further undescribed alternate embodiments may be available for a portion, is not to be considered a disclaimer of those alternate embodiments. One of ordinary skill will appreciate that many of those undescribed embodiments incorporate the same principles of the disclosure as claimed and others are equivalent. 

What is claimed is:
 1. A bolt carrier group for a firearm comprising: a gas key including a first and second screw holes, a gas passage and at least a first shear absorption component on the gas key; and a bolt carrier having a gas hole, a first and second screw holes arranged to align with the first and second screw holes of the gas key and adapted for receiving a screw in each screw hole for securing the gas key to the bolt carrier, and at least a second shear absorption component on the bolt carrier arranged to engage the first shear absorption component of the gas key.
 2. The bolt carrier as recited in claim 1 wherein the first shear absorption component and the second shear absorption component comprise a recoil lug and a recoil lug slot.
 3. The bolt carrier group as recited in claim 2 wherein the recoil lug is a protrusion having a cross-section shape in the form of a rounded rectangle, and the recoil lug slot is one of a detent or hole having side walls in the form of a rounded rectangle sized to receive the recoil lug.
 4. The bolt carrier group as recited in claim 1 wherein the first shear absorption component is a recoil lug slot and the second shear absorption component is a recoil lug.
 5. The bolt carrier group as recited in claim 3 wherein the recoil lug is a protrusion having a cross-section shape in the form of one of a square, rectangle, circle, or T and the recoil lug slot is one of a detent or hole having side walls in the form of one of a square, rectangle, circle or T selected and sized to receive the recoil lug.
 6. The bolt carrier group as recited in claim 1 wherein the bolt carrier includes a plurality of shear absorption components adapted to engagement a plurality of shear absorption components on the gas key.
 7. The bolt carrier group as recited in claim 1 wherein the bolt carrier extends from a first end to a second end to define a first longitudinal axis, and wherein the gas key extends from a first end to a second end to form a second longitudinal axis, wherein when the gas key is fixed to the bolt carrier second so that the second longitudinal axis is parallel to and in space relation with the first longitudinal axis.
 8. The bolt carrier group as recited in claim 7 wherein the first shear absorption component and second shear absorption component are arranged to engage and transfer force in a direction parallel to the first longitudinal axis and second longitudinal axis during operation of the bolt carrier group.
 9. The bolt carrier group as recited in claim 7 wherein the first shear absorption component and second shear absorption component do not prevent the gas key from moving in a direction perpendicular to the first longitudinal axis or second longitudinal axis.
 10. The bolt carrier group as recited in claim 1 wherein the first and second shear absorption components do not fixedly secure the gas key to the bolt carrier.
 11. The bolt carrier group as recited in claim 2 wherein the recoil lug is integrally molded in one of the gas key or the bolt carrier.
 12. The bolt carrier group as recited in claim 2 wherein the recoil lug is a removable pin protruding from one of the gas key or the bolt carrier.
 13. A bolt carrier group for a firearm comprising: a gas key having a first and second screw holes and a recoil lug arranged along a bottom surface, and a gas passage extending from a forward facing inlet portion at a front portion of the gas key to a downward facing outlet portion on the bottom surface adjacent one of the first or second screw holes, wherein the recoil lug is integrally formed with the gas key, disposed between the first and second screw holes, extends downwardly from the bottom of the gas key and has a cross-sectional shape in the form of a rounded rectangle; and a bolt carrier having a first and second screw holes, a recoil lug slot and a gas hole arranged along an upper surface of the bolt carrier, wherein the first and second screw holes are arranged to align with the first and second screw holes of the gas key and are adapted for receiving a screw in each screw hole for securing the gas key to the bolt carrier, and wherein the recoil lug slot is integrally formed in the bolt carrier upper surface, shaped in the form of a rounded rectangle and sized and arranged to receive and engage the recoil lug of the gas key, and wherein the gas hole of the bolt carrier is arranged to align with the outlet of the gas passage on the bottom surface of the gas key. 